Four-stage filtration system



FIG. 1 is a front-top-left perspective view of the four-stage filtrationsystem showing our new design;

FIG. 2 is a front elevational view thereof, wherein the rear elevationalview is identical thereto;

FIG. 3 is a right elevational view thereof, wherein the left elevationalview is identical thereto;

FIG. 4 is a top plan view thereof; and,

FIG. 5 is a bottom plan view thereof.

The broken lines shown in the figures are for the purpose ofillustrating portions of the four-stage filtration system and form nopart of the claimed design.

CLAIM The ornamental design for the four-stage filtration system, asshown and described.